The behaviour of the order parameter and its effects in intrinsically-layered superconductors are studied within a continuous Ginzburg-Landau model. A simple model of interlayer coupling is proposed in which we suggest that the coupling strength between superconducting and insulating layers may be qualitatively described by a reciprocal of a difference between the order parameters at the respective layers. The feasibility of such an approach is demonstrated by considering Hussey's magnetization experiments, the case of Tc depression observed in iodine-intercalated and Pb-substituted Bi2Sr2CaCu2O8+δ, and some other properties and experiments in layered superconductors.